[GHC] #9698: GHC_PACKAGE_PATH should be more lenient for empty paths

[GHC]

#9698: GHC_PACKAGE_PATH should be more lenient for empty paths
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       Reporter:  Fuuzetsu           |                   Owner:
           Type:  feature request    |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:
     Blocked By:                     |  None/Unknown
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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 Consider a working {{{GHC_PACKAGE_PATH=foo:bar:baz:}}}.

 It is not uncommon that we would want to append som extra vars later which
 might possibly be empty, perhaps resulting in
 {{{GHC_PACKAGE_PATH=foo:bar:baz::qux:}}}. Unfortunately, due to the
 {{{::}}} GHC tries to looking for a package at the empty path and shows
 the usual error about not being able to find the package. This forces the
 user to set up various safeguards (such as {{{${GHC_PACKAGE_PATH:+:} }}}
 bashism) at the inital binding location.

 It'd be great if GHC would simply skip over empty paths.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9698>
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